I need to vent!

I am 20 weeks pregnant, and I can already tell this is going to be a struggle with my mother in law. My husband is an only child, and they are very close as she had him when she was young. My MIL is only 43 and always wanted another child, but her now husband is unable to and she brings it up all the time. I have always felt bad for her because of this, but now that I am pregnant all she talks about is that she's "jealous of me".. she's said a few comments too like "I'm going to love it when I'm at the grocery store with the baby and people think I'm the mom" or "I think I'll buy a crib for our house and decorate a room for him there too." CRINGE

Any advise?? I'm sure her heart is in the right place but I'm crawling out of my skin when she says that my son, her grandchild, will be just like another son for her! she's very "my way or the highway" so I'm worried about her ignoring my ways of raising this child when I'm not around.. or even worse in front of my face and disrespecting me since I'm a new mother and she's done this before.

my husband notices it too but says "she's just excited" or "it'll be better when the baby is here" but I'm going crazy!! advice??